Ro is in my top ten favourite characters for sure.
In fairness, there were some half-hearted attempts to introduce other recurring female characters. I'm not sure why most of them only lasted one or two episodes: Commander McDougal (Brooke Bundy wasn't available for the episodes they needed her), Selar, Sonia Gomez, Robin Lefler (Ashley Judd was on the up and couldn't be persuaded to skip more mainstream parts), or Ensign Rager (Lanei Chapman had much greater range as seen in Space, Above and Beyond).
It's curious that male guess stars seem to have more longevity. I think it's partly because they are less defined by their gender (i.e. less likely to be deemed worthy as a fleeting love interest of a male character) Selar was touted as a possible love interest for Worf - what the hell - and was another medical doctor - what the hell - in a show that was lacking scientific characters of all sorts. What a waste.
I think Troi suffered from this mindset. Until much later in the show's run, Troi-centric episodes revolved around her getting a love interest, her mother, or her empathy. Despite being a Lt-Commander with diplomatic credentials of her own, she never got any episodes that focused on her skills as a diplomat, psychologist, or senior officer.
In Disaster, she was clueless about how the ship was run - very insulting. Sirtis was also frustrated that she never got any action scenes unless she was possessed. I wish they'd given Sirtis more input into her characterisation. I bet she would have livened up Troi from the start .